Method of making composition friction elements



Patented Jan. 7, 1936 UNITED. STATES METHOD OF MAKING COMPOSITIONFRICTION ELEMENTS John D. Alley, Pittsburgh, Pa., assignor to AmericanBrakeblokcorporation, New York, N. Y., a corporation of New York:

No Drawing.

Original application August 22,

1929, Serial No. 387,818,,nw Patent No. 1,882- 702, dated October 18,1932. Divided and this application July 29, 1932, Serial No. 626,033 i 3Claims.

This is a division of my application Serial No. 387,818 filed August 22,1929,(now Pat. No. 1,882,702 Oct. 18, 1932).

The invention relates generally to the art of braking andmoreparticularly to the-manufac I ture of a novel friction element foruse in brakes,

clutches and other assemblies.

The object of the invention isv to provide a novel method of making acomposition brake element which is relatively rigid but yet hassufficient elasticity to enable it to be readily fitted to a brake heador shoe, a brake band, or other support.

And a further object of theinvention is to 5 avoid the necessity ofmaking composition brake elements accurately to conform with thecurvature of the support upon which they are mounted by providing animproved method of producing a novel element having a limited amount .ofinherent flexibility.

The invention is more especially useful in making composition brakeliners in strip form and in a generally arcuate shape to fit brake headsor shoes and brake bands or other supports, and I will describe theinvention as used for this purpose although it may also be used inmaking relatively thick brake blocks and other braking elements forvarious purposes.

It has been common practice heretofore to use a binder, generally adrying oil, in friction compositions, but it has not been practicable touse a sufficient amount of oil to produce a liner having any materialflexibility and at the same time thoroughly cure the liner in anyavailable commercial baking process. I have overcome this difficulty andhave enabled the use of a sufficient amount of oil to produce a.relatively flexible liner by adding sulfur to the composition mixture. Ihave added sulfur in the proportion of from 2% to 20% by weight of theamount of oil in the composition. For example, to 18 parts of, oil Ihave added sulfur over a range from 0.36 part to 4.5 parts and I havefound that added sulfur in the proportion of 15% of the amount of oilpresent appears to be the most desirable proportion to use. That is tosay 3 parts of sulfur are added to 20 parts of drying oil. When lessthan 15% of sulfur is used there is apt to be some difficulty inproperly curing the material; if more than 15% of sulfur is used theexcess will distill out and be lost. Diiferent compositions may enableor require a variation in the proportion of sulfur to oil and differentbinders may enable or require similar variations in the sulfurproportion. In all cases, however, it is desirable to use as much addedsulfur as the amount 'of binder will permit without adversely affectingthe curing step. To increase the flexibility of the-finishedproductsmall quantities, up

to 5 parts, of castor oil, cylinder stock oil, rosin, 5 freefatty acids,or like materials, may be added to the mixture.

The following is an example of a composition which may be used in makinga friction liner embodying my invention. '10

Parts Asbestos, short fibre Pyrobituminous material, such as bitumin-Binder, such as rawlinseed oil 18 15 Sulfur, 15% by weight of oil 2.7

In practicing my improved method I prefer to proceed as follows:-Thesulfur is first added to the oil and mixed by stirring; the oil-sulfur20 mix is then added to bitmuminous coal and mixed; then the asbestos isadded, and the whole is thoroughly mixed in any suitable mixing machine.I use ordinary flowers of sulfur or other finely divided sulfur,comminuted bituminous 5 coal, and short fibre asbestos. Other quantitiesof these materials and other mixing procedure may be employed which willproduce results equivalent to the materials and procedure indicated. 3

The mixture, without heating, can be rolled into a limp strip and cutinto sections for curing, or it can be made in block form in a moldunder pressure, and then cured or baked in an oven.-

A suitable heating schedule is four to five hours 35 at approximately F.and then five to six hours at approximately 300 F.

In quantity production it is desirable to cut the strip into sections ofstandard lengths as it comes from the strip machine and to place these40 sections upon arcuate forms by which they are supported in the curingoven. The limp sections will conform to the shape of the forms which arestandardized in a general way to the shape of heads or shoes or bands orother-sup- 45 ports in commercial use, or they may be easily pressed tothe forms and held thereon by means of clips. It is not necessary toshape the liner to the precise curvature of the support on which it isto be used because the liner has some flexi- 0 bility and can be shapedsnugly to the support in mounting it thereon. This applies to continuousstrip liners, which are referred to as such, as well as to those made inthe form of relatively short and thin blocks.

The composition may 55 ii A be molded in relatively thick blocks inaccordance with my invention and they will have the advantage of thatflexibility which my improved composition affords. The invention is ofspecial importance from a production standpoint because it enablesliners to be made quickly and at relatively low cost by rolling in acontinuous strip which can be cut up into sections of any lengthrequired; and it is also specially impor tant because it provides acomposition braking element having suflicient flexibility to enable itto be fitted to its support.

Where I have referred to the product of my invention herein as acomposition friction liner it is to indicate a useful embodiment, but itcan be made as a brake element in many different forms, including clutchfacings and the like, and in such sizes and shapes as may be required.

I claim: 7

1. The method of making a flexible composition friction element whichconsists in thoroughly mixing 18 parts of drying vegetable oil and 2.7parts sulfur with 25 parts finely divided pyrobituminous material andparts of short fibre asbestos, forming said mixture into shapes, andthen curing said shapes in a baking oven without pressure for four tofive hours at approximately F. and then for five to six hours atapproximately 300 F. to set the oil by sulfuration to bond theingredients of the element.

2. The method of making a flexible composi- 5 tion friction elementwhich consists in mixing suitable friction materials, an amount ofvegetable drying oil that will effectively bond the friction materialsafter curing and more than would be oxidized by heat in curing, andsufii- 10 cient sulfur to promote complete curing of the oil, formingthe mixture into a shape, and subjecting the shape to heat withoutpressure to cure the oil by sulfuration.

3. The method of making a flexible composi- 15 tion friction elementwhich consists in mixing suitable friction materials, an amount ofvegetable drying oil that will eifectively bond the friction materialsafter curing and more than would be oxidized by heat in curing, addingsul- 20 fur in the proportion of approximately 15% of the amount of oilpresent to promote complete curing of the oil, forming the mixture intoa shape, and subjecting the shape to heat without pressure to cure theoil by sulfuration. 25

- JOHN D. ALLEY.

